In diesel engines, especially those used in motor boats, the relatively high temperature of the fuel upstream of the fuel injection pump often prevents the development of full engine power. One reason is that the high temperature of the diesel oil reduces the engine output per liter of fuel, another that the diesel oil is partly vaporized due to partial pressure and friction effects in the line between the tank and the injection pump. These problems can be overcome by installing a fuel oil cooler in the fuel line ahead of the fuel pump, while further improvement can be achieved by installing an oil deaerator upstream of the fuel oil cooler.
Those fuel oil coolers which are available in the marketplace are relatively complicated to install, require a separate, low-temperature cooling water supply, and incur a high cost.